Profiling phenolic compounds in underutilized mango peel by-products from cultivars grown in Spanish subtropical climate over maturation course.

Nutraceutical market has undergone an exponential growth worldwide due to its health link-up. With the purpose of evaluating nutraceutical value, the phenolic composition of underutilized mango peel by-products of three cultivars ('Keitt', 'Kent' and 'Osteen') grown in Spanish subtropical climate was monitored at three maturation stages (green, ripe and overripe). Tracking the total phenol content, mango peels were figured out to have until twenty-seven fold higher than edible fraction. Mango peels comprised a wide range of phenolic compounds such as mono- and di-galloyl compounds, gallotannins, phenolic acids, benzophenones and flavonoids. The influence of both factors, cultivar and maturation degree, on the phenolic composition was the main outcome of the research. 'Keitt' mango peel was revealed as the cultivar with the highest phenolic content mainly due to the great quantities of galloyl glucose, 5-galloylquinic acid, digalloylquinic acid, hexagalloyl glucose and macluring galloyl glucoside detected. Regarding to the effect of maturation degree, green mango peels showed the highest amounts of polyphenols, although this behaviour could be dependent on the mango cultivar. Therefore, mango peels resulted to be a promising and low-cost resource of phenolic compounds to be exploited in food industry, but to enhance the nutraceutical value, factors such as cultivar and maturation degree should be taken into account.

HPLC-DAD-Q-ToF-MS profiling of phenolic compounds from mango (Mangifera indica L.) seed kernel of different cultivars and maturation stages as a preliminary approach to determine functional and nutraceutical value.

Mango seed kernel is a by-product which is usually discarded. However, it has been confirmed in this study that seed kernel exhibits more phenolic compounds with bioactive properties than edible fraction of mango. The influence of factors such as cultivar and maturation degree on the phenolic composition has been studied to evaluate nutraceutical value. The comprehensive analysis of phenolic composition by HPLC-DAD-Q-ToF-MS seed kernel from different cultivars ('Keitt', 'Kent'and 'Osteen') at five maturation stages was conducted. Results evidenced that 'Keitt' samples exhibited higher quantities of iriflophenone glucoside, maclurin C-glucoside, maclurin digalloyl glucoside, mangiferin, 5-galloyl quinic acid and trigalloyl glucose at the first three ripening stages. However, seed kernel from 'Osteen' variety showed higher amounts of hexa- and hepta-gallotannins whose concentrations diminished over the maturation course. Therefore, cultivar and maturation stage factors should be take into account due to their influence on the phenolic composition and subsequently on the nutraceutical value.

Pressurized GRAS solvents for the green extraction of phenolic compounds from hibiscus sabdariffa calyces.

An environmental friendly extraction procedure has been tested to extract phenolic compounds from H. sabdariffa calyces using pressurized GRAS solvents. A central composite rotatable design (CCRD) was performed to evaluate the influence of the main operational conditions: temperature (40-200 °C) and solvent composition based on aqueous hidroalcoholic solutions (0-100% ethanol). Phenolic composition of experimental extracts analyzed by HPLC-ESI-QTOF-MS showed that higher temperatures and greater ethanol percentages drove to solvents with lower dielectric constants, which resulted in extracts with major quantities of phenolic compounds. An exception was the extraction of cyanidin-3-sambubioside that could only be quantified in extracts performed at the lowest temperature (40 °C) due to its thermal sensibility. In addition, a RSM was carried out with the aim to maximize the extraction of total phenolic content. To this end, the predicted optimal extraction conditions by RSM were 200 °C and 100% (v/v) of ethanol. Results showed that temperature and ethanol percentage had a significant influence on the extraction of total phenolic compounds (p value < 0.05). The mathematical model pointed out 200 °C of temperature and 100% of ethanol as the optimum conditions to perform the isolation of phenolic compounds by means of pressurized GRAS solvents.

Lipid nanocarriers for the loading of polyphenols - A comprehensive review.

Polyphenols are secondary metabolites found in all vascular plants and constitute a large group of at least 10,000 unique compounds. Particular attention is currently being paid to polyphenols attributed to their beneficial effects in the protection and prevention of several diseases. While their use in food, pharmaceutical and cosmetic industries is largely documented, several environmental conditions (e.g. light, temperature or oxygen) may affect the physicochemical stability of polyphenols, compromising their bioactivity in vivo. To overcome these limitations, the loading of polyphenols into nanoparticles has been proposed aiming at both increasing their bioavailability and reducing eventual side effects. Lipid nanoparticles offer several advantages, namely their biodegradability and low toxicity, with the additional capacity to modify the release profile of loaded drugs. This paper is a review of the recent advances of lipid nanocarriers commonly used for the encapsulation of polyphenols, highlighting their added value to increase bioavailability and bioactivity of this group of compounds as well as their application in several diseases.

Enhanced and green extraction of bioactive compounds from Lippia citriodora by tailor-made natural deep eutectic solvents.

Natural deep eutectic solvents (NADESs) have been postulated as alternative green solvents for the isolation of valuable bioactive compounds from Lippia citriodora. Thus, 11 different NADESs, based on choline chloride (ChCl) as the hydrogen bond acceptor in combination with different hydrogen bond donors (organic acids, polyalcohols, sugars, and urea) were tested. According to the results obtained, ChCl-lactic acid exhibited the highest extraction yield for iridoids, 7.25 mg g-1, phenylpropanoids, 17.23 mg g-1, and flavonoids, 9.02 mg g-1 being significantly greater than phenylpropanoid and flavonoid yields, 15.63 and 5.43 mg g-1 respectively, extracted with methanol as conventional solvent. Subsequently, in order to optimise the most influential microwave assisted extraction (MAE) parameters, a Box-Behnken design paired with a response surface methodology were implemented. Temperature and water content showed a strong effect on the extraction of polyphenol sub-classes, while the effect of irradiation time was less noticeable on extraction yields. Temperature of 63.68 °C, a water content of 32.19% and a microwave irrdiation time of 17.08 min were the optimum conditions provided by the statistical program. The use of NADESs showed potential to facilitate the design and customisation of green tailor-made solvents which have greater extraction capacity than conventional organic solvents.

Reversed-phase ultra-high-performance liquid chromatography coupled to electrospray ionization-quadrupole-time-of-flight mass spectrometry as a powerful tool for metabolic profiling of vegetables: Lactuca sativa as an example of its application.

Lettuce (Lactuca sativa), a leafy vegetal widely consumed worldwide, fresh cut or minimally processed, constitutes a major dietary source of natural antioxidants and bioactive compounds. In this study, reversed-phase ultra-high-performance liquid chromatography (RP-UHPLC) coupled to electrospray ionization-quadrupole-time-of-flight mass spectrometry (ESI-QTOF-MS) was applied for the comprehensive profiling of polar and semi-polar metabolites from three lettuce cultivars (baby, romaine, and iceberg). The UHPLC systems allowed the use of a small-particle-size C18 column (1.8 µm), with very fine resolution for the separation of up to seven isomers, and the QTOF mass analyzer enabled sensitive detection with high mass resolution and accuracy in full scan. Thus, a total of 171 compounds were tentatively identified by matching their accurate mass signals and suggested molecular formula with those previously reported in family Asteraceae. Afterwards, their structures were also corroborated by the MS/MS data provided by the QTOF analyzer. Well-known amino acids, organic acids, sesquiterpene lactones, phenolic acids and flavonoids were characterized, e.g. lactucin, lactucopicrin, caftaric acid, chlorogenic acid, caffeoylmalic acid, chicoric acid, isochlorogenic acid A, luteolin, and quercetin glycosides. For this plant species, this is the first available report of several isomeric forms of the latter polyphenols and other types of components such as nucleosides, peptides, and tryptophan-derived alkaloids. Remarkably, 10 novel structures formed by the conjugation of known amino acids and sesquiterpene lactones were also proposed. Thus, the methodology applied is a useful option to develop an exhaustive metabolic profiling of plants that helps to explain their potential biological activities and folk uses.

Evaluation of different extraction approaches for the determination of phenolic compounds and their metabolites in plasma by nanoLC-ESI-TOF-MS.

Sample preparation is an important step for the determination of phenolic compounds in biological samples. Different extraction methods have been tested to determine phenolic compounds and their metabolites in plasma by nano-liquid chromatography coupled to electrospray ionisation-time-of-flight mass spectrometry (nanoLC-ESI-TOF-MS). The sample treatment optimisation was performed using commercial foetal bovine serum spiked with representative phenolic standards, namely naringenin, luteolin, verbascoside, apigenin, rutin, syringic acid and catechin. Different protein-precipitation conditions were evaluated as well as enzymatic digestion with trypsin and solid-phase extraction using different phases such as C-18, ABN and ENV+, working at different pH values. The optimum extraction procedure consisted of a previous protein-precipitation step using HCl 200 mmol/L in methanol for 2.5 h at 50 °C followed by a solid-phase extraction using C-18 cartridges at pH 2.5. This procedure was finally applied to the plasma of rats overfed with a phenolic-rich Lippia citriodora extract. These samples were analysed by nanoLC-ESI-TOF-MS, enabling the identification of five compounds previously found in the administered L. citriodora extract and one metabolite.

Comparison of different extraction procedures for the comprehensive characterization of bioactive phenolic compounds in Rosmarinus officinalis by reversed-phase high-performance liquid chromatography with diode array detection coupled to electrospray time-of-flight mass spectrometry.

In the present work, a comparative study between two environmentally friendly and selective extraction techniques, such as supercritical fluid extraction (SFE) and pressurized liquid extraction (PLE) have been carried out focusing in the bioactive phenolic compounds present in Rosmarinus officinalis. For the analysis of the SFE and PLE extracts, a new methodology for qualitative characterization has been developed, based on the use of reversed-phase high-performance liquid chromatography (RP-HPLC), equipped with two different detection systems coupled in series: diode array detector (DAD) and time of flight mass spectrometry (TOF-MS) detector connected via an electrospray ionization interface (ESI). The use of a small particle size C(18) column (1.8 µm) provided a great resolution and made possible the separation of several isomers. Moreover, UV-visible spectrophotometry is a valuable tool for identifying the class of phenolic compounds, whereas MS data enabled to structurally characterize the compounds present in the extracts. The applied methodology was useful for the determination of many well-known phenolic compounds present in R. officinalis, such as carnosol, carnosic acid, rosmadial, rosmanol, genkwanin, homoplantaginin, scutellarein, cirsimaritin and rosmarinic acid, as well as other phenolic compounds present in other species belonging to Lamiaceae family.

Identification of phenolic compounds from pollen extracts using capillary electrophoresis-electrospray time-of-flight mass spectrometry.

In this work, a new, easy and rapid method of analyzing phenolic compounds in pollen extract, based on capillary electrophoresis coupled with electrospray ionization time-of-flight-mass spectrometry (CE-ESI-TOF-MS), has been developed. A systematic investigation of separation parameters has been performed with respect to resolution, sensitivity, analysis time and peak shape. The electrophoretic parameters and electrospray conditions must be optimized to obtain reproducible analyses. Using this method, several important phenolic compounds such as acetin-glucoside, 7-O-methylherbacetin-3-sophoroside, galloyl-glucose, quercetin-3-sophoroside, apigenin-6,8-di-C-glycoside, quercetin-3-rutinoside, genistein-7-O-beta-D: -glucoside, luteolin-7-O-glucoside, apigenin-7-O-glucoside and 2',4',6'-trihydroxy-3'-formyldihydrochalcone have been determined directly from pollen extract. The efficiency, the rapidity, the small amounts of sample required, and the high resolution of CE coupled with the sensitivity, the selectivity, the accurate masses and the true isotopic patterns obtained using TOF-MS point to the potential of this approach for identifying the phenolic compounds present in pollen.

Advances in the analysis of phenolic compounds in products derived from bees.

Honey and propolis are rich in phenolic compounds, which act as natural antioxidants, and are becoming increasingly popular because of their potential role in contributing to human health. These compounds can also be used as indicators in studies into the floral and geographical origin of the honey and propolis themselves. We present here an overview of current analytical methods for measuring polyphenols in honey and propolis. The analytical procedure to determine individual phenolic compounds involves their extraction from the sample, analytical separation and quantification. The techniques reviewed are based on spectrophotometry as well as analytical separation techniques such as gas chromatography, high-pressure liquid chromatography and capillary electrophoresis.

Identification of phenolic compounds in rosemary honey using solid-phase extraction by capillary electrophoresis-electrospray ionization-mass spectrometry.

Complex extracts of rosemary honey constituents often require very effective separation techniques to allow the identification of different compounds. Capillary electrophoresis (CE) coupled to mass spectrometry (MS) detection can provide structure-selective information about the analytes in such matrices and has turned out to be an attractive alternative to HPLC methods. A simple and cost-effective analytical method involving solid-phase extraction (SPE) and capillary zone electrophoresis coupled to electrospray ionization-ion trap mass spectrometry (CZE-ESI-MS) to identify and characterize phenolic compounds in rosemary honey is described. The SPE, CE and ESI-MS parameters were optimized in order to maximize the number of phenolic compounds detected and the sensitivity of their determination. All CE-ESI-MS experiments were performed with uncoated fused-silica capillaries and an alkaline volatile buffer system consisting of 100 mM NH(4)Oac with 10% of 2-propanol at pH 10. Since sheath liquids can made significant effects on the sensitivity in typical CE-ESI-MS application, the effect of type and flow rate of the sheath liquid on the sensitivity of phenolic compounds were investigated. As result, the best sensitivity was obtained with a sheath liquid containing 2-propanol/water 60:40 (v/v) and 0.1% (v/v) of triethylamine at 3 microL/min in the negative ion mode. We describe the first method for the analysis of phenolic compounds in rosemary honey at mg/L levels by using a simple SPE before CE-ESI-MS analysis.

Interfacing capillary electrophoresis and surface-enhanced resonance Raman spectroscopy for the determination of dye compounds.

The at-line coupling of capillary electrophoresis (CE) and surface-enhanced resonance Raman spectroscopy (SERRS) was optimized for the separation and subsequent spectroscopic identification of charged analytes (dye compounds). Raman spectra were recorded following deposition of the electropherogram onto a moving substrate. To this end a new interface was developed using a stainless steel needle as a (grounded) cathode. The outlet end of the CE capillary was inserted into this metal needle; CE buffer touching the needle tip served as the electrical connection for the CE separation. A translation table was used to move the TLC plate at a constant speed during the deposition. The distance between the tip of the fused silica column and the TLC plate was kept as small as possible in order to establish a constant bridge-flow, while avoiding direct contact. The dyes Basic Red 9 (BR9), Acid Orange 7 (AO7) and Food Yellow 3 (FY3) were used as test compounds. After CE separation in a 20 mM borate buffer at pH 10, after deposition, concentrated silver colloid was added to each analyte spot, followed by irradiation with 514.5 nm light from an argon ion laser to record the SERRS signal using a Raman microscope. Different types of silver colloids were tested: Lee-Meisel type (citrate), borate, and gold-coated silver. BR9 (positively charged) gave much more intense SERRS spectra than the two negatively charged dyes. For BR9 and AO7 the citrate-coated Lee-Meisel colloid yielded the most intense SERRS spectra. The CE-SERRS system was used to separate and detect the negatively charged dyes. Silver colloid and nitric acid (to improve adsorption) were added post-deposition. Even though their chemical structures are very similar, AO7 and FY3 could be readily distinguished based on their SERRS spectra. The limits of detection (S/N = 3) of the CE-SERRS system ranged from 6.7 x 10(-5) M (2.6 x 10(-12) mol injected) for FY3 down to 1.8 x 10(-6) M (7.0 x 10(-14) mol injected) for BR9.